Cutters having face-sharpened cutting blades have been used for many years in processes for producing gears, particularly spiral bevel and hypoid gears and the like.
Face mill cutters of the form-relieved face-sharpened type comprise a plurality of cutting blades extending in an axial direction from one side of a cutter head with the cutting blades usually arranged and spaced equidistantly about the cutter head. The cutter head itself is adapted to be secured to the rotary cutter spindle carried by a machine tool. Each cutting blade includes a front face and a cutting edge formed by the intersection of the front face with the top and side surface of the cutting blade. A clearance edge is also present on the front face with the clearance edge being relieved from the cutting edge by a particular rake angle.
The cutting blades, which are usually releasably secured to the cutter head, may be blades known as outside blades which cut the concave side of the teeth of a work gear, or, the blades may be those known as inside blades which cut the convex side of the work gear teeth. Examples of face mill cutters having outside blades and face mill cutters having inside blades are shown in U.S. Pat. No. 3,192,604 to Whitmore. Alternatively, cutting blades and cutter heads may be of unitary construction, formed from a solid body of material such as high speed steel.
Another type of face mill cutter is shown by U.S. Pat. No. 3,268,980 to Blakesley et al. wherein cutters for roughing and cutters for finishing are shown in which both outside and inside cutting blades are alternatively arranged about a cutter head. This type of cutter forms the entire tooth slot between adjacent teeth on a work gear since each pair of inside and outside blades forms the opposite sides of adjacent teeth.
As with any cutter, continued use of form-relieved face mill cutters causes the cutting blades to become dull and therefore they must be periodically sharpened. It therefore becomes necessary to sharpen each blade by removing an amount of stock material from the front face of each blade thus removing the worn cutting edge and forming a new sharpened edge at the intersection of the newly formed front face and the top and one side surface of the blade. The side and end faces on the cutting blades used in form-relieved face mill cutters are helicoids. When the front face surface is removed for sharpening purposes, the new front face profile has the same shape and radial position relative to the cutter axis as the prior profile; but, it is displaced axially toward the back of the cutter. When dealing with a set of blades mounted in a cutter head, they must all be equally spaced and the sharpening planes must all have equal spacing.
One method of sharpening form-relieved type cutting blades is disclosed in U.S. Pat. No. 3,136,093 to Deprez in which a grinding wheel is traversed side-to-side across the width of the cutting face of a cutting blade.
Another known sharpening process for face-sharpened cutting blades is disclosed by U.S. Pat. No. 2,828,583 to Carlsen et al. in which a grinding wheel is oscillated across the cutting face of a cutting blade with each grinding stroke following a different path than the preceding stroke. The stated purpose of this method is to reduce or eliminate burrs of the cutting edge.
Yet another known sharpening process for face-sharpened cutting blades comprises feeding a grinding wheel in a straight line along the height of blade face, from the top of a cutting blade to the base of the blade face. In an opposite manner, a grinding wheel may be fed into the face of a cutting blade at the base of the blade face and then traversed along the height of the face to the top of the blade.
In the above described methods, burrs at the cutting edge are prevalent after sharpening. The burrs are generally tightly adhered to the cutting edge. Even after deburring operations, usually comprising lightly stroking the cutting edge with a soft steel or brass bar, remnants of the burrs remain. The tightly adhered burrs are believed to be caused by a welding action that takes place at the cutting edge largely due to excessive heat build-up caused by the grinding operation.
It is an object of the present invention to provide a method for sharpening face-sharpened cutting blades wherein any burrs formed at the cutting edge are reduced in size with those burrs present being loosely bonded to the cutting edge and easily removed by subsequent deburring operations.